Alarm systems are known which include a number of switches each connected to an identification module and through common wires to a controller. The controller is capable of determining which switches are tripped or malfunctioning by obtaining identification data from the identification module associated with any tripped or malfunctioning switches.
FIG. 5 shows such an alarm system wherein a controller 110 is connected through wires 102, to various digital input identification modules 104, some of which are connected to switches 106, while others are connected to loads 108. One drawback with such an alarm system is that it is limited to switches or other digital devices and does not provide for analog input.
It would be desirable to provide a single-wire loop alarm system which is capable of processing analog input.